1. Technical Field
This invention relates generally to document copiers having an exposure platen at which original pages are scanned, and more particularly to such copiers which allow the operator to scan each page individually on the platen before copying begins.
2. Background Art
There are known copiers which have exposure platens from which original pages are scanned to convert the images thereon to a series of digital data signals for use by a marking engine to produce collated copy sets of the original document. The original pages may be advanced to the exposure platen by an automatic document feeder, or the operator may place each original page individually on the platen. Some copiers provide both, so that the operator can choose the most convenient form.
In some such copiers, the operator is provided with "special features" options to adjust the images that are to be produced. For example, a designated original document (referred to herein as a "special page") to be copied may be placed face up on an exposure platen, whereat a wand is used by an operator to identify locations on the original document which define an area for special treatment such as screening, erase, annotation, spot coloration (also called "accent coloring"), relocation in the page format, etc.
Copiers are also known that include a multiple-page buffer memory for electronically storing scanned image data and printing instructions for a plurality of pages of a job. The stored pages can be printed as often as desired to produce a plurality of collated copy sets. In known copiers, the first copy set is produced as the original pages are scanned, edited, and sent to buffer memory.
There are several disadvantages to this procedure. Whenever the marking engine is operating to produce a copy set, there is a risk of malfunction (say, a paper jam) which would result in a shut-down of the marking engine and require operator attention. Any such malfunction as the operator is in the process of scanning original pages and programming the apparatus with special feature instructions for each special page, would tend to confuse the operator, slowing recovery from the malfunction situation and producing a risk of error when the operator resumes the scanning operation.
Another disadvantage of the conventional system relates to the amount of time that it takes an operator to scan original pages and program the apparatus with special feature instructions for each special page. High-speed electrostatographic copiers have a "skip cycle" mode in which the marking engine continues to operate until the image for the next page to be printed is available. In the skip cycle mode, the marking engine continues to run, but without paper feed, and with appropriate adjustment to charging, toning, erasing, and cleaning processes. Extended skip cycling while an operator scans original pages and programs the apparatus with special feature instructions for each special page wastes energy and causes undo wear and tear on the marking engine. On the other hand, shutting down the marking engine and restarting it between pages can cause long-term reliability problems.